The present invention relates to pins for the positioning and production of parts made of composite material and glued together used in tools for lamination and gluing of aircraft parts.
Tools for production of parts made of composite materials or glued together for aircraft are substantially cradles that contain the various parts of an group during the assembly step of a group itself. Said cradles form seats for precise positioning of the various parts so as to favour proper constraint thereof to the other parts of the group itself resting on the cradle.
It is known that in a cradle in which a part of an aircraft is housed both in the assembly step and for checks for setting-up and routine monitoring of the aircraft, pins are used for positioning and provisionally fixing loose or pre-assembled parts of the aircraft both during the assembly step and during setting-up of the aircraft itself.
The pins are inserted into purposely provided holes arranged in key points of the parts where a temporary fixing is necessary. During the step of production of parts made of composite materials, the pins create, where they are positioned, holes for future references for the assembly step on subsequent frames for assembly of the aircraft itself.
The pins notoriously comprise two parts: a cylindrical body and a head. According to the known art the aforesaid pins are made of resistant materials of a metal type or a plastic type, for example Teflon, and the process for the production of said pins comprises, amongst other things, a step of turnery of the aforementioned materials.
As known to the person skilled in the art, said step of the process entails very long and costly production times.
Furthermore, the use of metal materials for making said pin can damage the structure of the aircraft when the pin is totally inserted into the holes, because of relative movements between the structures of the frame or else on account of an incorrect insertion of the pin into the hole by the operator.
It should moreover be emphasized that said pins are used for fastening materials with different physical characteristics.
During the steps of polymerisation, usually hot polymerisation, with a thermal delta even of 170° C., different degrees of thermal expansion are produced between the various components or between the components of aircraft structures and the polymerisation cradles, according to their own coefficients of thermal expansion, which put said pins to non-negligible forces, due to the relative movements between the parts or between the parts and the equipment.
Said forces can also cause deformation of the engagement hole with consequent deformation also of said pins, making them difficult to extract and no longer further usable.
As in the production of an aircraft said pins are used in a wide range of production steps, the aforementioned problem leads to an increase in the costs caused, very frequently, by the unusability of pins already adopted in the previous steps of production of the component and of the aircraft itself.
Extraction of said pins, once they have been inserted into the reference holes, is complex and can be at times particularly difficult, and in some cases can lead indirectly to damage of the tool itself.
The known art does not provide a satisfactory solution and, it is necessary to rely only upon the experience of the operators for carrying out said operation.